1. Field of the Invention
The present invention relates to a fuel quantity estimation apparatus for estimating the quantity of fuel in a fuel tank mounted in a vehicle in accordance with a traveling state of a vehicle.
2. Description of the Related Art
A technique for estimating the quantity of fuel in a fuel tank mounted in a vehicle has hitherto been known.
JP-A-2006-47100 is mentioned as a literature showing an example of such a technique.
As shown in FIG. 3, JP-A-2006-47100 discloses that a fuel level correction section (66A) of control means (66) makes a correction to a power value output from a fuel level gauge (50) through filtering (see descriptions provided in paragraphs [0025] to [0027] in JP-A-2006-47100).
JP-A-2006-47100 also discloses that a primary filter exhibiting high response performs filtering correction after a first set time has elapsed since an ignition switch (96) was turned on and that a secondary filter exhibiting low response performs filtering correction after elapse of a second set time (see descriptions provided in paragraphs [0027] to [0032] in JP-A-2006-47100).
However, the degree of undulation of fuel in a fuel tank changes from time to time due to vibrations experienced by a vehicle, and under the technique of JP-A-2006-47100 difficulty is encountered in appropriately estimating the quantity of the fuel stored in the fuel tank.
As shown in FIG. 1,according to the technique of JP-A-2006-47100, the secondary filter is used for any one of cases where the engine of a vehicle is started, where a vehicle is running, and where the engine of the vehicle is stopped. Therefore, there is a potential of occurrence of a situation in which a difference between the quantity of fuel actually stored in a fuel tank and an estimated value acquired by means of filtering correction cannot be disregarded.